The present invention relates to an image display device for projecting and displaying an image from an image generation source on a larger scale onto a rear projection type screen. The invention also relates to the rear projection type screen used in the image display device, a Fresnel lens sheet used in the screen, and a method of making the Fresnel lens sheet.
An image display device which enlarges, using a projection lens, an image displayed on a small-sized image generation source and projects the image onto a rear projection type screen has recently been improved remarkably in image quality. Incidentally, a cathode-ray tube or a liquid crystal display may be used as the small-sized image generation source. The above-mentioned type of image display device has been becoming more and more popular for both home and business use.
The image display device uses a reflecting mirror for reflecting an enlarged image provided from a projection lens and conducting it to the rear projection type screen, thereby decreasing the depth of the device. The rear projection type screen used in the image display device is usually provided with a Fresnel lens sheet and a lenticular lens sheet. The Fresnel lens sheet converts an enlarged projection image into light which is substantially parallel or light which faces somewhat inwards. The lenticular lens sheet diffuses an image light horizontally of the screen. In such a screen, to attain a further reduction in thickness of the image display device, the configuration described for example in WO/02/27399 (Patent Document 1) is known.